In monopolar electrosurgical cutting a current is allowed to pass from an active cutting electrode through a patient's tissue and into a grounding pad or cable. The current cuts tissue at the active cutting electrode, the cutting rate being dependant on current density through the tissue in that area. At low current density heat is generated but no cut is achieved. At high current density fast cutting occurs.
In bipolar electrosurgical cutting the current passes from the active cutting electrode through the patient's tissue to a return electrode which is located in, or is in contact with, the patient's tissue a short distance away from the cutting electrode. The cutting and return electrodes are generally carried by a single instrument.
Current density depends on the applied electrical power (measured in watts) which can be controlled utilizing an adjustment present on a conventional generator designed for this purpose. The current density also depends on the series impedance of the overall circuit Series impedance is equivalent to the sum total of the resistance to the current throughout the circuit. It is affected by the material and the design of the active electrode, by the patient, by the type of tissue to be cut, and by the condition of contact established between the patient and (when a monopolar electrode is utilized) the grounding pad as well as by the location of the grounding pad relative to the cutting site. During surgery, the generator setting is usually adjusted to compensate for this variability and to reflect the surgeon's preference. Generators used in this type of surgery have a wide range of power outputs to accommodate a variety of procedures and devices.
The objective in electrosurgical cutting is to heat the tissues cells so rapidly that they explode into steam leaving a cavity in the cell matrix. The heat is meant to be dissipated in the steam rather than be conducted through the tissue to thereby dry cut adjacent cells. When the electrode is moved and fresh tissue is contacted new cells are exploded and the incision is made. Such electrosurgical cutting involves the sparking of the current to the tissue. The current utilized is in the radio frequency range and operates by the radio frequency current jumping across an air gap to the tissue. This is known as sparking.
An explanation of electrosurgical cutting theory can be found in the FORCE 1 Instruction Manual published by Valleylab of Boulder, Colo. on Mar. 1, 1986. The entire text of the FORCE 1 Instruction Manual is incorporated herein by reference.
An advantage touted for electrosurgical cutting is that adjacent tissue is not supposed to become overly heated and thereby desiccated and damaged. Thus, what one desires is a clean cut without damage to adjacent tissue. Unfortunately, current electrosurgical cutting electrodes are of a construction such that sufficient heating of adjacent tissue does occur it is somewhat damaged and desiccated.
Electrosurgical fulguration/coagulation operates similarly but at different power levels and using shorter bursts of higher peak voltages as discussed on page 5 of the FORCE 1 publication.
The present invention is directed to overcoming one or more of the problems as set forth above.